1. Field of the Invention
The present invention relates to a jet stream injection system in a fluidized-bed type heat exchanger.
2. Description of the Prior Art
In most of prior-art systems, a fluid runs in a single-phase flow on a heat exchanging surface both in high-temperature heat exchange and low-temperature heat exchange when a heat exchanger is operated, and in many cases, fins are fitted on the heat exchanging surface so as to form a coil with fins, since the rate of heat transmission between the heat exchanging surface and the fluid (gaseous body) such as air is low. However, the coil with fins costs much to manufacture, and moreover an increase in a heat exchanging area is accompanied by a disadvantageous increase in the size of an apparatus. Furthermore, in an operation of the heat exchanger at low temperature, defrosting must be conducted frequently when frost is formed on an evaporator with fins, and the heat exchanger must be made large-sized, taking this operation into account, whereby the cost is further increased.
FIG. 17 illustrates one example of a priorart refrigeration or heat pump cycle. In the figure, numeral 4 denotes a casing of a heat exchanger of an air heat source type, 1 a heat transmission coil of the heat exchanger provided in said casing 4, i.e. an evaporator coil or a condenser coil each provided with fins, 10 a compressor, and 9 a heat exchanger (condenser and evaporator). When a cycle is made to operate as a heat pump, in other words, when the heat transmission coil 1 is made to operate as the evaporator coil, a refrigerant running from the compressor 10 to the heat exchanger (acting as the condenser) 9 through a discharge pipe 11 emits heat to a fluid flowing in an inlet 14 and out of an outlet 15 and is liquified. The liquefied refrigerant flows into the heat exchanger through an expansion valve 8, absorbs heat from the outside air sucked in through the lower part of the heat exchanger casing 4 by a far. 16, and is thereby evaporated and sucked again into the compressor 10 via a suction pipe 13. When frost is formed on the surface of the heat transmission coil of the heat exchanger, it is melted by a liquid (water) injected from a defrosting injection pipe 6, and the mixture water thus formed is gathered in a water tank positioned in the lower part and is discharged outside through a pipe 7. In some cases a defrosting system using a hot gas (not shown in the figure) is employed instead of the liquid injection defrosting system.
Although a flow of piping in the shifted direction in a refrigerating (cooling) system in which the element denoted by 1 operates as a condenser of an outside air heat source and the element denoted by 9 as an evaporator is not shown in this figure, the system shown herein can be made to operate both for a heat pump cycle and a refrigeration cycle.
It is also known publicly that the employment of a heat exchanger of a fluidized-bed type as a prior art makes excellent the efficiency of heat transmission when the heat exchanger operates at high temperature.
FIGS. 18 and 19 illustrate one example of a prior-art heat exchanger of the fluidized bed type, in which numeral 4 denotes a casing of the heat exchanger, and 1 a heat transmission coil of the heat exchanger provided in said casing 4, which is formed as a coil with fins. Numeral 2 denotes a fluidized bed. The fluidized bed 2 is formed in a space ranging from the position of the coil with fins to the position of a surface 28 sufficiently above, and it is constituted by particles (glass particles or the like) and supported in the aforesaid casing 4 by a net 3 with a mesh smaller than the size of said particles. A waste hot gas of high temperature flows in through an inlet 26, passes through the meshes of the net via an air chamber 5 and blows out through the entire region of the fluidized bed 2 from the lower part thereof, making the fluidized bed 2 be fluidized. A liquid (e.g. water) flowing through the heat exchanger 1 absorbs heat from the waste hot gas and the fluidized particles of high temperature through the solid-state contact of these substances with the coil of the heat exchanger, thus turning to be of high temperature. The waste hot gas flows out of an outlet 27.
The air chamber denoted by numeral 5 is provided for equalizing the distribution of the static pressure of air so as to make good a mixed-phase flow in the fluidized bed.
The waste hot gas blows out through the net 3 formed entirely of meshes (a minute-hole plate with a large number of holes distributed uniformly may also be employed), according to the above-stated prior art. On the other hand, the coil with fins of the heat exchanger extends in the longitudinal direction, and therefore it is hard to attain a stable and uniform fluidized state when the height of the fluidized bed is small, which tends to cause channeling (a phenomenon of blowing-through of an airflow) in a part of the fluidized bed 2.
This causes a fault that the heat transmission of the coil 1 turns nonuniform in time and space, which makes the coil inefficient. Therefore, the surface 28 of the fluidized bed 2 must be positioned high enough to enlarge the height of the bed, in order to make excellent the rate of heat transmission of the whole of the heat transmission coil of the heat exchanger, and this involves an increase in the blowing pressure of the waste hot gas and also an increase in power required therefor.
Moreover, defrosting must be conducted by a hot gas method or a liquid injection method when frost is formed on the heat exchanger in FIG. 17, and this operation produces a negative effect on the refrigerating capacity of a refrigerator or the heating capacity of a heat pump, causing also a time loss.
The present invention aims to eliminate the faults of the above-described prior art, which are summarized in the following.
The prior-art heat exchanger is provided with the coil with fins on the gas side thereof, and the gas side of the heat exchanger of this type is inferior in the rate of heat transmission, and thus it needs to be made large in size inevitably. Even with the fins provided, the apparatus needs to be made large in size, which causes a disadvantage of high cost. Although there is a method in which the heat of an exhaust gas or the like is collected by the heat exchanger of the fluidized-bed type under a high temperature, the pressure loss of the bed is large when the height of the fluidized bed is large, and thus an enormous power is required for a blower.
Moreover, while the heat transmission coil of the heat exchanger is disposed in the longitudinal direction, holes for injection of gas positioned under the coil are the meshes of a net or the minute holes made in a plate and are entirely uniform, and consequently the circulative movement of particles in the fluidized bed is not smooth and tends to be instable, which makes it difficult to improve the rate of heat transmission as expected. Therefore, the heat exchanging performance of the heat exchanger of this type is not improved so much as expected, although it is generally put to practical use. In the fluidized bed whose height is small, on the other hand, channeling tends to take place, and by this phenomenon of local blowing through, a gas to fluidize the particles is let to leak out in vain.
Defrosting of the heat transmission coil in the air type heat exchanger, which is conducted by using a hot gas or sprinkled water, causes the lowering of the refrigerating capacity of a refrigerator or the heating capacity of a heat pump, while causing a time loss. The growth of frost on an evaporator causes the lowering of the heating capacity of heat pump in winter, and this is the largest cause that prevents the heat pump heating from being used widely in cold districts, and it is the most serious fault of a heat pump for saving energy.